Porsche Cayenne S E-Hybrid first drive review

German brand's new plug-in hybrid SUV makes sense for city slickers

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Porsche Cayenne S E-Hybrid first drive review

23 Oct 2014Greg Kable

Porsche has overhauled the hybrid drive system available with its second-generation Cayenne, adding a larger capacity battery that can be recharged via plug-in means rather than simply on the run, bestowing the new-to-the-range S E-Hybrid with a far more credible electric range along with stronger performance and vastly improved combined economy than the S Hybrid it replaces.

The modified petrol-electric system, similar to that brought to the Panamera S E-Hybrid last year and offered as an alternative to the Cayenne's recently upgraded range of petrol and diesel powerplants, is based around the Audi-sourced supercharged 3.0-litre V6 direct-injection petrol engine used by Porsche's earlier non-plug-in hybrid set-up.

The carry over combustion engine continues to produce 245kW and 440Nm of torque, but it is now mated to a more powerful electric motor mounted within the forward section of the new Cayenne S E-Hybrid's standard eight-speed automatic gearbox housing. The disc-shaped unit possesses 36kw more than that used by the discontinued Cayenne S Hybrid at 70kW, together than an added 10Nm of torque at 310Nm.

Altogether, Porsche's third dedicated plug-in hybrid model after the 918 Spyder supercar and plush Panamera S E-Hybrid, offers a combined system output of 306kW at 5500rpm along with a 590Nm of torque on a band of revs between 1200rpm and 4000rpm – all of which is permanently channeled to all four wheels via a mechanically-operated Torsen torque sensing four-wheel drive system rather than the multi-plate clutch system used by other more conventional petrol and diesel powered Cayenne models.

This provides the Cayenne S E-Hybrid with 27kW and 10Nm more than that the old Cayenne S Hybrid, which offered a combined 279kW and 580Nm.

Energy for the larger electric motor is provided by a new lithium-ion battery. Mounted underneath the luggage compartment, the liquid cooled unit has increased by 9.1kW in capacity over the nickel-metal-hydride battery used by Porsche's older hybrid system at 10.8W/h. A socket underneath the fuel flap allows the new battery to be charged on regular household mains power at either 3.6kW or, using an optional high voltage charger, a faster 7.2kW. The former provides a recharge time of 3.5 hours with the latter taking a claimed 1.5 hours.

The Cayenne S E-Hybrid is most effective when left to its own devices in Hybrid mode, at which its electronics continually alter the drive processes to provide optimum efficiency. However, it is possible to choose electric only running by pressing the E-Power button on the centre console. This is also the default mode at start up and, with a fully charged battery, is claimed to provide a zero emission range between 18km and 36km depending on how much of the electric motor's 70kW you are using, the topography of the road and a range of other factors, including the state of the air conditioning system.

In electric mode with 70kW and 310Nm, the Cayenne S E-Hybrid is claimed to accelerate to 60km/h in 8.9sec and run to a top speed limited to 125km/h, making it a convincing proposition – and not just in urban driving conditions.

With prodigious torque the moment your foot brushes the accelerator, the electric motor provides the new Porsche SUV with urgent step-off qualities, a flexible delivery and acceptable in-gear performance to the sort of speed limits in place in Australia – all without any tail pipe emissions.

But as much fun as it is to experience the instant acceleration supplied by the electric motor away from traffic lights, this sort of driving quickly depletes the limited electric range. The real benefit to all electric running is refinement. Gliding along on electric power alone, you quickly become aware of other sources of road noise, not least of all the Cayenne S E-Hybrid's substantial 245/50 front and 275/45 profile 18-inch tyres. Our test car also boasted a synthetic sound generator which filled the engine bay with fake engine noise – as specified under US regulations.

When the electric charge of the battery drops to less than 20 per cent or when your speed tops 125km/h, the hybrid system automatically switches to E-charge mode. So configured, the Cayenne S E-Hybrid's electric motor acts as an alternator as the petrol engine is engaged to provide both primary propulsion and electrical energy to charge the battery.

The driver can also choose this mode via a press of a button on the centre console. This is especially useful for journeys that end in cities with emission charging in place, allowing to you save the battery charge for when it is needed most.

On the open road, another driving mode, Sport, combines the power from both the electric motor and combustion engine to provide the Cayenne S E-Hybrid with its maximum 306kW and 590Nm. Although the new hybrid system adds a further 110kg to the kerb weight at 2350kg, the combined reserves are sufficient to provide the new Porsche with genuinely impressive performance – as evidenced by the claimed 0-100km/h time, which has improved by 0.6sec over the the old Cayenne S Hybrid at 5.9sec. Top speed has also increased incrementally at 243km/h.

Big gains have been achieved in fuel economy on the European test procedure. Porsche's official figures point to a whopping 5.1L/100km improvement at 3.1L/100km, with CO2 emissions dropping by 122g/km to just 79g/km. However, this does not take into account the energy used to charge the battery. Still, with an indicated 6.2L/100km over a combination of German autobahn driving and country roads, the Cayenne S E-Hybrid is extraordinarily frugal for something so big.

The facelifted second-generation Cayenne is a very convincing proposition with an impressively broad range of capabilities, something that has only been enhanced by its new plug-in hybrid system. If the majority of your driving is carried out in stop/start city conditions and you have easy access to a charger, the S E-Hybrid could be your ideal mode of transport.